1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, and a process cartridge and an electrophotographic apparatus each having the electrophotographic photosensitive member.
2. Description of the Related Art
Electrophotographic photosensitive members are each basically formed of: a photosensitive layer on which an electrostatic latent image is to be formed by charging and exposure; and a conductive support on which the photosensitive layer is to be provided. At present, semiconductor laser has been mainly used as a light source in an electrophotographic apparatus using any one of the electrophotographic photosensitive members, and investigations have been conducted on the potential of materials sensitive to the oscillatory wavelength of the semiconductor laser, i.e., around 790 nm, which is a relatively long wavelength, to find applications in charge-generating substances for use in the charge generation layers of the electrophotographic photosensitive members. Of the materials, such organic pigments as described below each of which is sensitive to light having a long wavelength have been frequently used: various metal phthalocyanines such as aluminum chlorophthalocyanine, chloroindium phthalocyanine, oxyvanadyl phthalocyanine, chlorogallium phthalocyanine, magnesium phthalocyanine, and oxytitanium phthalocyanine; and metal-free phthalocyanines.
The following procedure has been performed with a view to improving the characteristics of each of the electrophotographic photosensitive members such as developing performance: an intermediate layer is provided between the conductive support and the photosensitive layer. Each of the following resins has been known to serve as a material of which the intermediate layer is formed: polyamide (Japanese Patent Application Laid-open No. Sho 58-95351), polyester (Japanese Patent Application Laid-open No. Sho 52-20836), a vinyl acetate-ethylene copolymer (Japanese Patent Application Laid-open No. Sho 48-26141), chlorinated ethylene (Japanese Patent Application Laid-open No. 2005-10591), a maleic anhydride ester polymer (Japanese Patent Application Laid-open No. Sho 52-10138), polyvinyl butyral (Japanese Patent Application Laid-open No. Sho 57-90639), and a quaternary ammonium salt-containing polymer (Japanese Patent Application Laid-open No. Sho 51-126149). In addition, the intermediate layer has been formed by: dissolving any such resin in a solvent to prepare an application liquid for an intermediate layer; applying the liquid to the support; and heating the applied liquid.
However, each of those resins has high hygroscopicity in many cases because the resin has a functional group having large polarity in its molecular chain. In addition, the resistance of each of the resins varies to a large extent depending on the humidity of the ambience surrounding the resin. Therefore, when the intermediate layer is formed of any one of those resins alone, an increase in residual potential of each of the electrophotographic photosensitive members and fluctuations in electrical characteristics of each of the electrophotographic photosensitive members under a low-temperature, low-humidity environment, or high-temperature, high-humidity environment occur, and the extent to which image defects are alleviated is insufficient.